Optical throughput condenser

ABSTRACT

An optical throughput condenser re-concentrates light thereby causing light which otherwise would be wasted outside of the useful AΩ product, also known as optical throughput, of an illuminating system to be redirected back into the useful AΩ product. The optical throughput condenser includes a thin film having an angle gate such that light striking the surface with a range of incident angles such that the angle of incident is less than or equal to the gate angle (Θ GATE ) transmits through the thin film. Light striking the surface with a range of incident angles such that the angle of incident is grater than the gate angle. reflects back from the thin film. An integrating sphere is positioned such that light reflecting back from the thin film is directed towards the integrating sphere so that the light is redirected towards the angle gate.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application cross-references and incorporates by referenceU.S. Provisional Patent Application No. 60/397,514, filed on Jul. 18,2002 and entitled “Throughput Condenser”.

BACKGROUND

[0002] 1. Technical Field

[0003] The present invention relates to an optical throughput condenserthat re-concentrates light. More specifically, the invention overcomesillumination inefficiencies by causing light which otherwise would bewasted outside of the useful optical throughput AΩ of an illuminatingsystem be redirected back into the useful AΩ.

[0004] 2. Background Information

[0005] In an illumination or optical system, “throughput” means opticalthroughput. At any position within an optical system, optical throughputequals the product of the beam area (A) and the solid angle Ω subtended.Optical throughput or AΩ product is also sometimes referred to as theFrench word “étendue” or “etendue”.

[0006] Traditionally, the AΩ product is constant or invariant in alloptical or illumination systems. It cannot be lost or gained; it ispreserved. In optical or illumination systems, light beams can bemodified by various elements such as lenses and mirrors. Both the beamarea and angular substance can be modified. However, the product of thebeam area and the angular substance is always constant or invariant.This is the AΩ product.

[0007] The intention or goal of an illumination system is to get someamount of light from a particular source to a particular object in needof illumination. It is understood, similar to general optical systems,the AΩ product is invariant in illumination systems. In reality,however, it is often the case that efficiency is actually lost due tofactors such as system absorption.

[0008] Since it is well known that the AΩ product ultimately limitsperformance of illumination or optical systems, it is desirable todiscover systems and methods to increase the AΩ product for illuminationor optical systems.

SUMMARY

[0009] The present invention is an optical throughput condenser thatre-concentrates light. The optical throughput condenser overcomesillumination inefficiencies by causing light which otherwise would bewasted outside of the useful AΩ product of an illumination system to beredirected back into the useful AΩ product.

[0010] An optical illuminating system of the present invention includesan illuminating source that provides sharply defined angular range ofemitted light. Light is emitted from an output port when a thin filmdielectric angle gate is deposited on a transmissive substrate. Theangle gate has a sharp angularly dependent transmission such that aportion of light striking the thin film with an angle of incidence lessthan or equal to the gate angle transmits through the thin film and aportion of light striking the thin film with an angle of incidencegreater than the gate angle reflects back from the thin film. Anintegrating sphere is positioned in relationship to the thin film suchthat the portion of light reflected back from the thin film is directedtowards the integrating sphere. The portion of light directed toward theintegrating sphere is eventually redirected toward the angle gate. Afinal product of light of the optical illuminating system equals alllight portions striking the thin film and transmitted through the thinfilm, thereby defining the useful AΩ product.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Preferred embodiments of the invention, illustrative of the bestmode in which Applicant has contemplated applying the principals, areset forth in the following description and are shown in the drawings andare particularly and distinctly pointed out and set forth in theappended claims.

[0012]FIG. 1 is a side plane view of a thin film substrate.

[0013]FIG. 2 is a sectional view of the present invention including athin film substrate and an integrating sphere.

[0014]FIG. 3 is a sectional view of an alternate embodiment of thepresent invention including a thin film substrate and an integratingsphere.

[0015] Similar numerals refer to similar parts throughout the drawings.

DETAILED DESCRIPTION

[0016] The present invention is an optical throughput condenser. Ingeneral, the invention is a system and method that re-concentrateslight. More specifically, the invention is a system and method thatcauses light which would be otherwise wasted outside of the useful AΩproduct of an optical or illumination system to be redirected back intothe useful AΩ product.

[0017] The AΩ product is equal to the product of beam area A and solidangle Ω. Ω is based upon the angle of incidence of a surface and isdefined as the solid angle Ω within which a beam of light or a portionof light transmits through a film, rather than reflects back from thefilm. The beam area A is equal to the surface area of a particularsubstrate or thin film. The optical throughput condenser of the presentinvention re-concentrates light which otherwise would be wasted outsideof the useful AΩ product of an illumination system back into the usefulAΩ product by employing and combining two separate techniques. The firsttechnique is a thin film design with a sharp angularly dependenttransmission. Light striking a surface with an angle of incidence (AOI)higher than some design value reflects back, away from the thin film.Conversely, light within the AOI transmits through the thin film. Thethin film is employed as a gate allowing the portion of light strikingthe thin film within the AOI to transmit through thin film.

[0018] The second technology is an integrating sphere. An integratingsphere is a realization of the ideal perfectly Lambertian,non-absorbing, confined scattering volume. In the present invention,light which does not pass the angle gate of the thin film is directedback into the integrating sphere. Light will randomly bounce arounduntil it is either directed back into the gate or input port, oreventually absorbed by the overall system.

[0019]FIG. 1 is a side plane view of a thin film. Substrate 100 includesa thin film coating 102 having angle gate 104. Area A is defined as thesurface area of thin film coating 102 and/or substrate 100. Thin filmcoating 102 can be any low absorptive or dielectric design providing asharp cutoff between reflected and transmitted light at a design AOI.Likewise, substrate 100 can be any substrate capable of efficienttransmission, including, but not limited to, fused silica or commonoptical window materials. Ω is the solid angle within which a beam orportion of light transmits through substrate 100 and thin film coating102, rather than reflects back from thin film coating 102. Θ_(GATE) isthe axi-symmetric one-dimensional relationship associated with the solidangle Ω such that Ω=2π[1−cos(Θ)] angle equal to one-half of Ω. Lighttransmissions having an AOI less than or equal to Θ_(GATE), such aslight transmissions 106 and 107, are transmitted through thin film 102via angle gate 104 and substrate 100 to a final desired destination.Conversely, beams or portions of light having an AOI greater thanΘ_(GATE), such as light transmission 108, are not transmitted throughangle gate 104 and are reflected back away from thin film coating 102(towards the top of FIG. 1).

[0020] In prior art illumination systems, theoretically, all lighttransmissions similar to light transmission 104 would be transmittedthrough angle gate 104 of thin film coating to a final desireddestination. In a best-case scenario with prior art designs, this wouldbe the case. However, it is understood that some light transmissions areeventually absorbed by the overall system.

[0021]FIG. 2 is a sectional view of the present invention including athin film and an integrating sphere. FIG. 2 illustrates opticalillumination system 110 that incorporates the present invention andincludes substrate 100, previously shown in FIG. 1, in conjunction withintegrating sphere 120. It is understood that substrate 100, shown inFIG. 2 represents substrate 100 shown in FIG. 1 and is defined by theprevious discussion with reference to FIG. 1. Integrating sphere 120includes sphere 122, input port or gate 124, output port or gate 126,and coating 128. FIG. 2 also includes external illumination source 130,as well as light transmissions or beams of light 132, 134, and 136.

[0022] As shown in FIG. 2, external illumination source 130 is capableof transmitting various light transmissions into integrating sphere 120.However, only two such light transmissions are shown in FIG. 2 forclarity purposes. Light transmission will bounce off of the innersurface of sphere 122. At some point, the light transmissions forexternal illumination source 130 will eventually transmit towardssubstrate 100 having thin film coating 102 and angle gate 104 (shown inFIG. 1). If a particular light transmission or beam of light strikesthin film coating 102 of substrate 100 at an AOI less than or equal toΘ_(gate), the light transmission or beam of light will transmit throughsubstrate 100 and thin film 102 via angle gate 104 to a final desireddestination. However, if a particular light transmission or beam oflight strikes thin film coating 102 of substrate 100 at an AOI greaterthan Θ_(gate), the light transmission does not transmit through anglegate 104, but rather is reflected back within integrating sphere 120.The particular light transmission will then bounce off of the innersurface of sphere 122 until it is either absorbed by the system or isagain transmits towards thin film 102 and substrate 100. Once again, ifthe particular light transmission transmits at an AOI less than or equalto Θ_(gate), the light transmission will transmit through substrate 100and thin film coating 102 via angle gate 104. Conversely, if the lighttransmission strikes substrate 100 with an AOI greater than Θ_(gate),the light transmission will be reflected back within integrating sphere120 and will again bounce within integrating sphere 120 until it iseither eventually absorbed by the system or strikes thin film coating102 of substrate 100 for another attempt to transmit through substrate100 and thin film coating 102.

[0023] In one embodiment, coating 128 includes micro retro reflectorssuch as ScotchLight Balls™ to nearly reverse incident redirection. Microretro reflectors are often used to concentrate light in a particulardirection, rather than scattering light in every direction. Inparticular, the balls reflect light to return back in the direction fromwhence the light came, no matter what the incident direction or angle.Micro retro reflectors of the present invention are quasi-retroreflectors in that they have some angular spectrum. In other words, if abeam of light or light transmission is shined on the micro retroreflectors of the present invention at a particular angle, a smallamount of the light is scattered; however, most of the light reflectsback in a direction close to the direction from whence the beam of lightcame, but not perfectly. The beam of light or light transmission mayreturn slightly off in angularity, such as up 5°. By controlling thediameter, index, and range of site of the micro retro reflectors, theangularity from the incident direction can be controlled. Micro retroreflectors may be incorporated into all portions of coating 128, or maybe incorporated into spatially distinct portions of coating 128 toincrease efficiency.

[0024]FIG. 3 is a sectional view of an alternate embodiment of thepresent invention including a thin film and an integrating sphere. FIG.3 illustrates optical illumination system 210 which includes integratingsphere 220 having sphere 222, output port 226, and coating 228. FIG. 3also includes internal illumination source 230, as well as lighttransmissions 232, 234, and 236, and substrate 100, shown and describedwith reference to FIG. 1.

[0025] Optical illumination system 210, shown in FIG. 3 differs fromoptical illumination system 110, shown in FIG. 2, in that opticalillumination 210 includes internal illumination source 230, rather thanexternal illumination source 230. Having internal illumination source230 does not change the concept of the present invention, however,having an internal illumination system, such as internal illuminationsystem 230, can reduce an escape route (input port or gate 124 of FIG.2) in which beams of light or light transmissions may escape integratingsphere 220 without reaching the desired final destination. It isunderstood that optical illumination systems 110, 210 willre-concentrate light to improve the overall light transmissions of an AΩproduct.

[0026] It is also understood that both an external illumination sourceand an internal illumination source, such as external illuminationsource 130, and internal illumination source 230 may be used withoutvarying from the present invention. In addition, any number of internaland/or external illumination sources may be utilized.

[0027] The illumination systems and the optical throughput condensersshown and described with reference to FIGS. 1-3 are capable ofre-concentrating light such that portions of light or lighttransmissions which otherwise would be wasted outside of the useful AΩproduct of an illumination system are redirected back into the useful AΩproduct, thereby increasing the useful AΩ product without increasingeither the beam area or angle Ω.

[0028] Accordingly, the invention as described above and understood byone of skill in the art is simplified, provides an effective, safe,inexpensive, and efficient device, system and process which achieves allthe enumerated objectives, provides for eliminating difficultiesencountered with prior devices, systems and processes, and solvesproblems and obtains new results in the art.

[0029] In the foregoing description, certain terms have been used forbrevity, clearness and understanding; but no unnecessary limitations areto be implied therefrom beyond the requirement of the prior art, becausesuch terms are used for descriptive purposes and are intended to bebroadly construed.

[0030] Moreover, the invention's description and illustration is by wayof example, and the invention's scope is not limited to the exactdetails shown or described.

[0031] Having now described the features, discoveries and principles ofthe invention, the manner in which it is constructed and used, thecharacteristics of the construction, and the advantageous, new anduseful results obtained; the new and useful structures, devices,elements, arrangements, parts and combinations, are set forth in theappended claims.

What is claimed is:
 1. An optical throughput condenser comprising: atransmissive substrate an angle gate created via a thin film dielectriccoating deposited on the transmissive substrate such that light strikingthe coated surface with a range of gate angles less than or equal to thegate angle transmits through the thin film, while light striking thecoated surface with a range of gate angles greater than the gate anglereflects back from the thin film; and an integrating sphere positionedsuch that light reflecting back from the thin film is directed towardsthe integrating sphere so that the light is subsequently redirectedtowards the angle gate.
 2. The optical throughput condenser of claim 1,wherein the angle gate is defined by an angle of incidence of the thinfilm.
 3. The optical throughput condenser of claim 1, wherein the thinfilm has a sharp angularly dependent transmission.
 4. The opticalthroughput condenser of claim 1, and further comprising: a final productof light equaling all light striking the thin film within the angle gateand transmitted through the thin film.
 5. The optical throughputcondenser of claim 1, and further comprising: a plurality of micro retroreflectors positioned on a portion of the integrating sphere.
 6. Theoptical throughput condenser of claim 5, wherein the plurality of microretro reflectors are positioned on the portion of the integrating sphereto substantially reverse an incident ray direction of the lightreflected back from the thin film.
 7. The optical throughput condenserof claim 1, and further comprising: an illuminating source positionedwithin the integrating sphere.
 8. The optical throughput condenser ofclaim 1, and further comprising: a first illuminating source positionedoutside of the integrating sphere; and a second illuminating sourcepositioned within the integrating sphere.
 9. An optical illuminationsystem comprising: an illuminating source providing a range of angles; atransmissive substrate an angle gate created via a thin film dielectriccoating deposited on the transmissive substrate such that light strikingthe coated surface with a range of gate angles less than or equal to thegate angle transmits through the thin film, while light striking thecoated surface with a range of gate angles greater than the gate anglereflects back from the thin film; an integrating sphere positioned suchthat light reflecting back from the thin film is directed towards theintegrating sphere so that the light is subsequently redirected towardsthe angle gate; and wherein the portion of light directed towards theintegrating sphere is redirected towards the angle gate.
 10. The opticalillumination system of claim 9, and further comprising: a final productof light equaling all light angles striking the thin film within therange of gate angles and transmitted through the thin film.
 11. Theoptical illumination system of claim 9, and further comprising: aplurality of micro retro reflectors positioned on a portion of theintegrating sphere.
 12. The optical illumination system of claim 11,wherein the plurality of micro retro reflectors are positioned on theportion of the integrating sphere to substantially reverse an incidentray direction of the portion of light reflected back from the thin film.13. The optical illumination system of claim 9, wherein the illuminatingsource is positioned within the integrating sphere.
 14. The opticalillumination system of claim 9, and further comprising: at least oneadditional illuminating source positioned within the integrating sphere;and wherein the first illuminating source is positioned outside of theintegrating sphere.
 15. A method of reconcentrating light within anoptical illumination system, comprising: transmitting a series of lightangles from an illuminating source; directing the series of light anglestowards a thin film such that a first portion of light is transmittedthrough an angle gate of the thin film and a second portion of lightreflects back from the thin film; redirecting the second portion oflight towards the angle gate; generating a final product of lightequaling all light portions transmitted through the angle gate; andwherein the total amount of power concentrated in the AΩ product oflight is greater than in an original AΩ product.